Influenza

Presented By: Dr. Md. Salequr Rahman

Dep. Of Community Medicine

Influenza

•Acute Respiratory Tract infection caused by influenza virus, A, B and C.

•Known pandemic caused by A.• Sudden onset of chills, malaise, fever,

muscular pain and cough.•Truly an international disease. May occur in

pandemics every 10-15 years due to major antigenic changes. In between pandemics, epidemic may occur at intervals of 2-3 years.

•At present 3 types of influenza viruses are circulating in the world: A(H1N1), A(H1N2) and B Viruses.

Avian influenza:

•Large group of different influenza viruses that primarily affect birds. H5N1 virus is a strain of pandemic potential. First infected human in 1997 in Hongkong.

•Agent: Type A, type B and type C.

•The influenza virus is unique among the viruses because it is frequently subject to antigenic variation. When there is a sudden complete or major change, it is called a “shift”.

•When the antigenic change is gradual over a period of time, it is called a “drift”.

•Reservoir of infection: Animals and birds-swine, horses, dogs, cats, domestic poultry, wild birds etc.

•Source of infection: Case or subclinical case. Usually droplet infection.

•Period of infectivity: 1-2 days before and 1-2 days after the onset of symptoms.

Host factors:

•Age and sex•Environmental

factors- season, overcrowding

Prevention:

•Good ventilation at public buildings, avoidance of crowded places during epidemics, cover the face with handkerchief, to stay at home at first sign of influenza.

•Vaccination- effective if administered two weeks before epidemic.

Prevention:

•Vaccines recommended for certain groups of people- in industry, for public services, elderly, persons with chronic diseases, HIV infected.

•Killed vaccine (immunity lasts for 3-6 months), annual revaccination is necessary/ live attenuated vaccine.